On a build of a Jenkins job, is it possible to change build parameters midway through?

Question

We are using Jenkins to automate several of our build and test processes. For some of our process, the engineer starting the build needs to specify a parameter. But the range of possible and optimal values for that parameter change throughout the course of the day.

What I would like to do is let the engineer specify a value - if they know an optimal value - or leave it blank and have a value be calculated by an early build step. If the value is calculated, I would like the calculating build step to update the parameter value of the job. That way, all subsequent build steps don't have to worry about using the parameter or calculating it, they just use the parameter regardless.

It looks like the Groovy Script Plugin might be able to do this, but I can't see how I can SET the build parameters, just GET them.

Answer 1

Found the answer: use the EnvInject Plugin. One of the features is a build step that allows you to "inject" parameters into the build job from a settings file. I used one build step to create the settings file, then another build step to inject the new values. Then, all subsequent build steps and post-build operations used the new value.

Update with an example:

To add a new parameter (REPORT_FILE), based on existing one (JOB_NAME), inject a map with new or modified parameters in the Groovy Script box:

// Setting a map for new build parameters
def paramsMap = [:]

// Set REPORT_FILE based on JOB_NAME
def filename = JOB_NAME.replace(' ','_') + ".html"
paramsMap.put("REPORT_FILE", filename)

// Add or modify other parameters...

return paramsMap

Answer 2

Jenkins does have the ability to parameterize builds. For a string parameter, the developer can leave the field blank and then your build scripts can check to see if the env. variable for the parameter is set. If the env. var. is not set, the script can perform whatever calculation is needed (I don't think Jenkins has "pre-build steps") and pass it along. For a choice parameter the first line can be something like (Default), and again the build script can test its value and act accordingly.

Note on (Default)

I tried leaving the first line of the choice box blank, and Jenkins saved it correctly the first time; but when I came back to reconfigure the build Jenkins ran some kind of trim on options and the leading blank line was removed so I settled on (Default).

I hope this helps,
Zachary